Denver International Airport (DIA) began enforcing a rule on Sunday that requires anyone interested in demonstrating to submit an application seven days in advance. The regulation was challenged by protesters, including one who recorded a video criticizing Denver Police Commander Tony Lopez for violating his First Amendment rights.

“Put all the signs away that have anything to do with first amendment expression, political message,” Lopez told demonstrators. “Based on legal advice we are getting at this time from the city attorney, what’s being displayed is a violation of airport rules and regulations.”

“I cannot carry the Constitution without a permit?” a protester asks. “Correct, according to airport rules and regulations,” Lopez responds.

After the video spread on social media, Heath Montgomery, a spokesperson for DIA, told a local reporter that the regulation is intended to protect airport patrons’ safety. “We have to ensure that people who use this airport are safe and able to go about their business uninterrupted and that’s going to remain our focus,” he said.

The U.S. Supreme Court has ruled that airports are not traditional public forums, so they can regulate people in ways that may seem to violate their First Amendment rights.

But the movement toward limiting protesters’ free speech rights is not confined to the terminals of DIA. In anticipation of an active protest movement during Trump’s administration, multiple Republican-controlled states are currently pushing for legislation that would discourage and even criminalize nonviolent, public demonstrations.

Chip Gibbons, the policy and legislative council for the Bill of Rights Defense Committee, wrote on his group’s website that he believes this proposed law violates the First Amendment.

“It is most likely unconstitutional, and if passed will have a chilling effect on speech as individuals will worry if they can be sued by the government for exercising their constitutional rights,” he wrote.

While they attempt to open up the laws to sue protesters, Minnesota Republicans are also considering a bill that would increase the potential penalty for nonviolent demonstrations. Introduced in early January and named the “Minnesota Public Safety Personnel Protection Act,” the legislation would mandate a penalty of no less than 12 months in prison and a fine of up to $10,000 to any protester that obstructs police or other public employees.

And in Michigan, Republican lawmakers are attacking both unions and protesters by pushing legislation that would increase fines against picketers to $1,000 per person per day of a picket and $10,000 per day for an organization or union involved in the picket. The bill passed the state House of Representatives in December, but was set aside by the Senate.

Law enforcement form a line across Interstate 94 on Saturday, July 9, 2016, in St. Paul, Minn., in response to protesters who blocked the highway in response to the death of Philando Castile. CREDIT: AP Photo/Joe Danborn

Taking a different tactic, four other states are considering anti-protest laws that would target demonstrators who protest on the streets, according to The Intercept. The bills have all been introduced in the last few months as responses to high-profile protests by Black Lives Matter activists and opponents of the Dakota Access Pipeline that shut down highways.

The Intercept summarized the bills that Republican lawmakers have proposed in North Dakota, Minnesota, Washington, and Iowa:

In North Dakota, for instance, Republicans introduced a bill last week that would allow motorists to run over and kill any protester obstructing a highway as long as a driver does so accidentally. In Minnesota, a bill introduced by Republicans last week seeks to dramatically stiffen fines for freeway protests and would allow prosecutors to seek a full year of jail time for protesters blocking a highway. Republicans in Washington state have proposed a plan to reclassify as a felony civil disobedience protests that are deemed “economic terrorism” … And in Iowa a Republican lawmaker has pledged to introduce legislation to crack down on highway protests.

Though Democrats in state legislatures may be able to block at least some of these bills, the flood of legislative proposals stemming from anti-protester sentiment is worrisome for civil liberties advocates. Lee Rowland, a senior staff attorney at the American Civil Liberties Union, told ThinkProgress she finds it “troubling” that states would prioritize anti-free speech legislation at the beginning of their legislative sessions.

“This is a marked uptick in bills that would criminalize or penalize protected speech and protest, and every person should be alarmed at that trend,” she said, calling the bills unconstitutional. “We should also be alarmed by the attitude they betray, which is that when Americans get out into the streets and make their voices heard — recently, in record numbers — their elected representatives’ response is not to listen to those concerns but to attempt to silence and criminalize them.”

“That goes against the very fabric of our constitutional democracy, and legislators introducing these bills should be ashamed,” she added. “To try to silence those who are speaking up right now is a betrayal of American values.”